The present invention relates to improved polyetherimide ester elastomeric compositions, and more particularly, to improved nucleated thermoplastic polyetherimide ester elastomer compositions having increased crystallization temperatures (T.sub.c), increased crystallization rates and reduced mold cycle time. These compositions are particularly useful for production of finished polymer products by such techniques as injection molding, blow molding, rotational molding and the like.
Thermoplastic polyetherimide ester elastomer compositions and the method of producing them are known in the art and are available from General Electric Company under the trademark LOMOD.RTM.J. These compositions have many excellent properties which make them particularly useful for extrusion and molding applications, including one or more of the following enhanced properties: stress-strain resistance, toughness/strength, and tensile set at low flexural modulus combined with rapid crystallization rates and excellent moldability as demonstrated by short cycle times and good mold releasability, respectively. Although the crystallization rates of the thermoplastic polyetherimide ester elastomer compositions are relatively rapid, it is always desirable to improve crystallization rates, increase crystallization temperature (T.sub.c) and reduce mold cycle time without substantially adversely effecting any other properties. Increases in T.sub.c, increases in crystallization rate and/or reduction in mold cycle time create substantial efficiencies in time and reduced costs in manufacturing processes.
The use of nucleating agents, also called crystallization improvers or crystallization promoters, to promote or enhance the crystallization of slowly crystallizable polyester resins such as, poly(ethylene terephthalate), is known. Nucleating agents, such as talc, in poly(ethylene terephthalate), have been used alone or have been combined with other polymers, such as polycarbonates, to make molding compositions having one or more improved characteristics or properties.
In one prior art embodiment, talc has been used as a crystallization promoting agent in very limiting amounts, that is, less than 1 part by weight. For example, in JP 80/52343 (published Apr. 16, 1980) and abstracted in Chemical Abstracts 93(14):133342e, there are disclosed crystalline polyester compositions of a polyester/polycarbonate copolymer with 0.3 part by weight of talc crystallization improver. In another reference, JP 81/32537 (Apr. 2, 1981), Chemical Abstracts 95(2):8330g; glass-reinforced polyester compositions for molding are prepared from poly(ethylene terephthalate) and 0.7 part by weight of talc. In JP 83/93752 (June 3, 12983, Chemical Abstracts 100(8):52546k, there are disclosed polyester molding compositions employing poly(ethylene terephthalate) and crystal nucleating agents, such as 1 part by weight of metal salts of aromatic oxysulfonic acids and/or talc. In JP 83/127756 (July 29, 1983), Chemical Abstracts 100(10):69288a, 0.5 part by weight of talc is employed in polyester molding compositions of poly(ethylene terephthalate) and polycaprolactone. In JP 83/129047 (Aug. 1, 1983), Chemical Abstracts 100(8):52575u, glass-reinforced polyester compositions are disclosed which contain poly(ethylene terephthalate), a condensation product of diphenyl ether or diphenyl thioether and a carbonyl compound, and 1.0 part by weight of a talc nucleating agent.
In another approach, high quantities of talc, in excess of 10 parts by weight, have been employed in polyester compositions. In U.K. 1,592,206, corresponding to German Offen. DE 2,755,950 (June 29, 1978), flame-retardant reinforced thermoplastic poly(ethylene terephthalate)/polycarbonate compositions are disclosed which have a concentration of 10-50% by weight talc and preferably 10-30% by weight talc to effect an appreciable increase in the arc track resistance of the composition. In JP 77/8059 (Jan. 21, 1977), Chemical Abstracts 87(2):68969g, a similar resin composition is disclosed which utilizes talc and/or SiO.sub.2 in a concentration range of 25-40% by weight. In JP 83/52343 (Apr. 15, 1983), Chemical Abstracts 99(22):176931n, 5 parts by weight of talc is used as a nucleating agent for polyester compositions of poly(ethylene terephthalate), poly(butylene terephthalate) and polycaprolactone.
In still other proposed compositions, intermediate amounts of a nucleating agent between 0.1 to 4-5 parts by weight have been employed in poly(ethylene terephthalate)/polycarbonate compositions. For example, in U.S. Pat. No. 4,587,272, Avakian et al. disclose foamable thermoplastic compositions of polycarbonate alone, or with poly(ethylene terephthalate), a foaming agent and 0.1 to 5.0 parts by weight of a foam nucleating agent to provide a surface for bubble formation. Among the suitable foam nucleating agents included in U.S. Pat. No. 4,587,272 are organic polymeric particulates further comprising an acrylate impact modifier. In EP 135904 (published Apr. 3, 1985), there are disclosed poly(ethylene terephthalate) moldable blends containing graft-modified rubber, 0.1-4.5%, and preferably 0.5-3.5% by weight, of talc, which is said to reduce warping. It has also been discovered by W. F. H. Borman and M. G. Minnick in copending U.S. application Ser. No. 948,275 filed Dec. 31, 1986 and entitled "Improved Nucleated Reinforced Polyester/Polycarbonate Molding Compositions" that the addition of from about 2 to about 10% by weight of talc, to reinforced blends comprising poly(ethylene terephthalate) and poly carbonates substantially improves the physical properties of the compositions and further that by including sodium dihydrogen phosphate in said compositions further improves the physical properties.
It has also been suggested that flexural modulus as well as other physical properties, may be enhanced by blending one or more thermoplastic polyesters with copolyetheresters. For example, Brown et al. in U.S. Pat. No. 3,907,926 disclose an improved copolyetherester and poly(butylene terephthalate)-containing blend which has high Young's modulus at room temperature and above and also possesses good low temperature impact strength and flexibility. Charles et al. in U.S. Pat. No. 4,469,851, disclose copolyetherester and polybutylene terephthalate (PBT) blends having superior melt stability. It has been suggested by Avery et al. in U.S. Pat. No. 4,212,791 that segmented polyester-polyether block copolymers behave synergistically with oligomeric polyester to improve crystallization temperature and rate in a composition having an inert particulate nucleating agent such as, talc, kaolin, CaCO.sub.3, Al.sub.2 O.sub.3, silica and graphite, and poly(alkylene terephthalate). Light et al. in U.S. Pat. No. 3,957,706 provide compositions having a sodium salt of a monocarboxylic acid and a polyetherester elastomer having good compression recovery after deformation and clearness. In U.S. Pat. No. 4,579,884 Liu has prepared blends of a copolyetherester, an aromatic thermoplastic polyester and a clay which are capable of absorbing high energy impact and withstanding high temperatures.
In many cases attempts to improve certain properties of a polyetherimide ester often have an adverse effect on other properties of the polyetherimide esters, and improvements in one property often result in a substantial sacrifice in the performance of the polymer because of the impact of a particular additive of agent on another property of the polymer. Frequently, when agents are used to enhance crystallization in a polyetherimide ester, there is a substantial impact on flexural modulus, i.e., flexural modulus is increased to unacceptable limits. Accordingly, it is desirable to improve the prior art nucleating agents and systems which increase crystallization rate, increase crystallization temperature (T.sub.c) and/or reduce mold cycle time without any substantial increase in flexural modulus.